add sx127x_txdone() function to poll for Tx done

Inc/sx127x.h

@@ -35,5 +35,6 @@ int32_t sx127x_rx(sx127x_t *sx127x, uint8_t *buf);
 int32_t sx127x_snr(sx127x_t *sx127x);
 int32_t sx127x_rssi(sx127x_t *sx127x);
 int32_t sx127x_rand(sx127x_t *sx127x);
+int32_t sx127x_txdone(sx127x_t *sx127x);
 
 #endif /* SX127X_INC_SX127X_H_ */

Src/sx127x.c

@@ -440,6 +440,18 @@ int32_t sx127x_rand(sx127x_t *sx127x)
 	return tmp;
 }
 
+int32_t sx127x_txdone(sx127x_t *sx127x)
+{
+	uint8_t irq;
+
+	/* read IRQ flags */
+	return_val_if_fail(sx127x_readbyte(sx127x, SX127X_REG_IRQFLAGS, &irq) == 0, -1);
+	/* clear the TXDONE flag */
+	return_val_if_fail(sx127x_writebyte(sx127x, SX127X_REG_IRQFLAGS, irq & ~SX127X_IRQFLAGS_TXDONE) == 0, -1);
+
+	return irq & SX127X_IRQFLAGS_TXDONE;
+}
+
 static int32_t sx127x_writebyte(sx127x_t *sx127x, uint8_t reg, uint8_t byte)
 {
 	uint8_t txdata[2] = { WREG(reg), byte };